1. Field of the Invention
The invention in general relates to the field of gear manufacture and in particular to a process which is supplemental to the normal grinding process performed on the gears.
2. Background Information
In the fabrication of large helical gears, such as may be used in ship propulsion systems, after the gear teeth are formed and heat treated, they are subjected to a grinding operation to eliminate slight inaccuracies.
The inaccuracies are extremely small, dimensionally measuring, in some instances, thousandths or even millionths of an inch; however even this amount is sufficient to set up undesirable noises at discrete frequencies. Accordingly, the gear teeth are subjected to a grinding operation to reduce or eliminate the inaccuracies.
A problem arises in the use of large grinding apparatus to reduce the inaccuracies in the helical gears in that the grinding apparatus itself may introduce slight errors, the most prominent of which is known as undulation errors. These errors are the source of both structure-borne and airborne noise which can exceed predetermined limits resulting in unacceptable gear performance, particularly for ship propulsion systems wherein the noise is transmitted through the water and may be detected at great distances.
The post-grinding finishing process of the present invention substantially reduces such undulation errors.